Crown-shaped pulley lagging

ABSTRACT

Pulley lagging comprising center and end members formed for mounting in end-to-end relation on and across the peripheral surface of a pulley parallel to the pulley axis. The members are formed with belt traction material having a constant thickness over the length of the center member and having an equal thickness at the abutting ends of the end members but tapering over the lengthwise dimension of the end members to a lesser thickness at the outer ends thereof.

llnited States Patent Holz Feb. 5, 1974 CROWN-SHAPED PULLEY LAGGING Prima Examiner-Charles J. M hre 76 1 1 w1111 c.1111 207w.v St., Y 1 men or g 2 2 me Assistant Examiner-R. H. Lazarus Attorney, Agent, or Firm-Manfred M. Warren et al. [22] Filed: Mar. 27, 1972 [21] Appl. No.: 238,185 [57] ABSTRACT Pulley lagging comprising center and end members [52] US. Cl. 74/230.7, 74/2305 formed for mounting in end-to-end relation on and [51] Int. Cl. Fl6h 55/48 across the peripheral surface of a pulley parallel to the [58] Field of Search 74/2305, 230.7 pulley axis. The members are formed with belt traction material having a constant thickness over the [56] References Cited length of the center member and having an equal UNITED STATES PATENTS thickness at the abutting ends of the end members but 2 847114 8/1958 Orr 74/2305 tapering the lengthwise dimension of the end 1:769:160 7/1930 74/230] members to a lesser thickness at the outer ends 3,140,621 7/1964 Stone 74/2305 thereof- 2,287,488 6/1942 Ross 74/2307 v 3,354,735 11/1967 1-1011 74/2301 5 Clams, 9 Drawmg figures Patented Feb. 5, 1974 2 Sheets-Sheet 1 O G) OQ O CROWN-SHAPED PULLEY LAGGING The invention relates to members added to the peripheral surface of belt driving pulleys for improving belt grip or friction, such as disclosed in U. S. Pat. No. 3,354,735.

Lagging of the character described, commonly rubber, may be directly vulcanized to the pulley surface or demountably secured thereto as disclosed in the aforementioned patent, the latter having the great advantage of permitting renewal when the lagging becomes worn or damaged. A further feature of the latter structure is that the lagging is made up of a plurality of elongated sections which are held on the pulley by fastening strips or guides disposing the traction sections across the width of the pulley, that is, parallel to its axis of rotation. Accordingly, individual sections may be replaced without disturbing the other sections disposed around the pulleyperiphery. Such an arrangement has enabled the manufacture of the traction sections under controlled production techniques ensuring sections of uniformly high quality. Also, the sections are made in standard lengths, as for example 6 feet, enabling the user to cut off the length of section required for his pulley, thus minimizing the amount of inventory required to be kept on hand by the user.

Aside from improving belt friction, another desirable feature of pulley design is the provision of what is known as crown in the pulley shape which affords belt training, that is, the retention of the belt on the pulley. Large sized belts are very expensive and, accordingly, belt life is of prime importance. Retention of the belt on the pulley is important, not only for traction purposes, but in preventing movement of an edge of the belt from the pulley where it may contact the supporting structure for the conveying system and damage the belt. Best known is the center crown system wherein the pulley tapers uniformly to the center plane of the pulley. While this structure is quite satisfactory with relatively narrow pulleys, it becomes increasingly difficult and expensive to accomplish as the pulley width increases. In large pulleys having a width of, say, 6 to 8 feet, center crowning is extremely difficult and expensive to accomplish. Furthermore, it is undesirable from the standpoint of belt life. The inherent large difference in diameter between the center of the belt and its edges causes a scrubbing action between the belt and the pulley, establishes an undue tension on the center of the belt and on lacings, and produces an uneven stress pattern which leads to premature belt failure.

Furthermore, the modular system, as disclosed in US. Pat. No. 3,354,735, does not work well in the provision of a crown form since it would require the production of different section forms for each different pulley width resulting in a prohibitively large number of manufacturing dies and number of different pieces required to be carried in stock. The important advantage of quality, low-cost production would thus be lost.

described hereafter, provides full pulley lagging life expectancy. Experience has demonstrated relatively minimum wear on the edge crown sections, thus providing an assembly having a life equal to the flat center section forming part of the lagging combination.

I have found that excellent belt training can be achieved with minimum belt wear by providing a flat center section on the pulley terminating in stepped down end sections and wherein the ratio of the length of the flat section to the total width of the belt is in the range of about 0.5 to 0.7 with about 0.6 considered as optimum. I have further discovered that by making each of the lagging sections of three pieces, it is possible to use a single center section of uniform shape cut to desired length in combination with a pair of identical pre-formed end sections to fit a wide range of pulley widths while retaining the belt-training-to-belt-life ratio within the above range. The combination of the foregoing discoveries thus makes possible the attaining of commercial mass production with attendant uniformly high quality and low costs; all of the advantages inherent in the modular mounting concept of US. Pat. No. 3,354,735; and long belt and lagging life accompanied by effective belt training. In other words, by means of the present invention, the usual flat pulley may be converted to an edge crown pulley with belt traction lagging applied thereto, a combination not heretofore available since it could be obtained only by expensive metal forming of the pulley or equally expensive and difficult machining of the lagging applied thereto.

The invention provides other objects and features of advantage, some of which of the foregoing will be set forth in the following description of the preferred form of the invention which is illustrated in the drawings accompanying and forming part of this specification. It is to be understood, however, that variations in the showing made by the said drawings and description may be adopted within the scope of the invention as set forth in the Claims.

Referring to said drawings:

FIG. 1 is an end elevation of a pulley having the lagging of the present invention applied thereto.

FIG. 2 is a fragmentary plan view of a portion of the pulley.

FIG. 3 is a fragmentary cross-sectional view taken substantially upon the plane of line 3-3 of FIG. 2.

FIG. 4 is a fragmentary cross-sectional view taken substantially on the plane of line 4-4 of FIG. 2.

FIG. 5 is a cross-sectional view of the pulley taken substantially on the plane of line 55 as shown in FIGS. 1 and 2.

FIG. 6 is a chart showing belt life versus belt training characteristics.

FIG. 7 is a fragmentary plan view of a modified form of lagging holding strip.

FIG. 8 is a cross-sectional view of the strip shown in FIG. 7 taken substantially on the plane of line 8-8 of FIG. 7.

FIG. 9 is a crossrsectional view of the lagging strip shown in FIGS. 7 and 8 taken substantially on the plane of line 99 of FIG. 7.

The crown-shaped pulley lagging or traction face structure of the present invention comprises briefly center and end components or modules 11, and 12 and 13 ofbelt traction material adapted for mounting on the peripheral surface 21 of a pulley in alignment across the pulley parallel to its axis of rotation; the center module 11 being formed to provide a substantially constant belt gripping diameter; and the end modules 12 and 13 being formed to provide a relatively reduced belt gripping diameter. The modules are formed with backing plates 16, 17 and 18 adapted for securing to the pulley surface 21 and with sections 26, 27 and 28 of belt traction material mounted on and substantially covering the plates; the thickness T of the center section being substantially constant over its dimension parallel to the pulley axis; and the thickness of end sections 27 and 28 being relatively reduced to provide the reduced belt gripping diameter. Preferably, end sections 27 and 28 have portions (see dimension FE in FIG. contiguous to the center module of a thickness substantially equal to the thickness T of the center section 26 extending the flat belt gripping line of said center section onto said contiguous adjacent portions of said end sections and with ends 31 and 32 of end sections substantially flush with adjacent ends 33 and 34 of the center section.

The essential characteristic of the present invention is the use of a standard thickness center section to obtain the flat belt gripping line in combination with the stepped down end sections which provide the desired edge crown belt training. The step down in the end sections may be rather abrupt or tapered over a part or over the full lengthwise dimension of the end sections, as depicted by the dimension EC in FIG. 5.

Normally, plates 16-18 are formed of steel and are fashioned with a transverse curvature fitting the curvature of the pulley surface 21. Sections 26-28 may be formed of natural or synthetic rubber or plastic vulcanized to the plates to provide a belt gripping or friction surface, and may be formed with sipes, as seen in FIG. 2, for improving the frictional grip on the belt.

.Pr. a y .t hs smbsrs re qfrs unaubl iz as viewed in plan in FIG Z, and contoured to the pulley face, as seeh iiiFliCiil, sofiiat when place d end to end,

they comprise a traction section covering a rectangular peripheral segment of the pulley thus affording a modular system with a plurality of three member combinations extending completely around the pulley circumference, as seen in FIG. 1. Conveniently, the width of the members is such that as a general rule the number of three member combinations required to surround a pulley will be equal to one-half of the diameter of the pulley. Thus, if the pulley has a diameter of 24 inches, twelve such three member combinations or traction sections would be required.

Any suitable means may be used for securing the three members 11-13 in end-to-end abutment so as to provide a substantially continuous and edge crowned belt gripping surface. The backing plates 16-18 may be secured to the pulley surface as by welding or bolting or by the use of attachment strips similar to that shown in US. Pat. No. 3,354,735. Plates 16-18 are here made somewhat larger than the corresponding widthwise dimension of sections 26-28 so that the plates will project from the sections at the circumferentially opposite sides thereof to provide side flanges 41 and 42 in the case of center member 1 1, and 43-44 for end member 12, and 45 and 46 for end member 13. The attaching means here comprises a plurality of elongated strips adapted for securing to the pulley surface 21 in parallel relation to the pulley axis and having a plurality of longitudinally spacedfirst portions 5l.po-

sitioned in abutment with the edge face of one of the flanges 4346 to drive the lagging; and a plurality of longitudinally spaced second portions 52 intermediate portions 51 and radially offset therefrom and positioned in overlying relation to the adjacent flange 41-46. Strips 48 may be conveniently stamped out of sheet metal whereby the strip may be blanked and formed in a single, low cost operation providing a plurality of longitudinally spaced openings 53 for facilitating the welding, screwing or bolting of the strips to the pulley face 21; a plurality of longitudinally spaced shoulders forming portions 51; and a plurality of longitudinally spaced overhanging and laterally projecting tabs forming the flange holddown portions 52. As will be observed, the tabs 52 provide with the pulley surface 21 a guideway for receiving flanges 41-46 thereby permitting the endwise sliding of the members 11-13 into position as illustrated. Preferably, end members 12 and 13 are secured in place. Openings 56 in these members may be provided for fastening, as by selftapping screws, or by turning up a part of flange 43-46 so as to engage one of the tabs 52, or by tack welding the backing plates to the pulley.

Where there is a variation in pulley circumference, usually in the order of 1 inch to 2 inches, a pair of half strips, as illustrated in FIG. 7, may be used, as shown in FIG. 1, for securing the circumferentially spaced apart ends of the members. The half strips 48a may be formed in the same manner as strips 48 with a series of longitudinally spaced openings 53a and with the longitudinally spaced shoulder and tab portions 51a and 52a but with the latter projecting from.one side only of the strip. Accordingly, a pair of such half strips may be mounted back to back but in circumferentially spaced relation, as illustrated in FIG. 1, to take up the space between adjacent lagging members 12a and 12b.

The flat belt gripping surface is denoted by dimension A in FIG. 5, and is the sum of the length of the center section 26 plus the flat extension length FE on the two end sections 27 and 28. This arrangement provides a uniform belt gripping action across the joint between adjacent ends 31-33 and 32-34. The provision of the flat extension FE on the end members also affects the dimensioning of these end members and the required length of the center section to obtain the desired belt-training-to-belt-life ratio. This relationship is depicted in the graph shown in FIG. 6 where A is the length of the flat surface of the lagging and B is the belt width. As will be observed from the chart, belt life is greatest when length A approaches length B, i.e. a flat pulley. On the other hand, belt training value is zero for a flat pulley and improves with the provision and extent of the crowned section. For belt training ability versus belt life, the optimum relationship of A to B is considered to be 60 percent. A good working relation, near optimum, is obtained for ratios of about 0.5 to about 0.7.

The foregoing characteristics make possible the attainment of the primary object of the present invention, viz., the ability to provide edge crown lagging on flat pulleys having a wide range of widths using a minimum number of standard size lagging members. For example, as shown in the table below, only two sizes of end members having lengths of 10 inches and 15 inches are required in combination with one standard center member to cover pulley widths ranging from 20 inches to 66 inches while maintaining the belt-trainingto-belt-life relationship at near optimum and within the range noted. The center members may be manufactured in standard lengths, as for example 6 feet, and then cut to required length by the user. Since the center module has a uniform thickness to provide the flat belt line, a number of such center pieces may be used in end-to-end abutment to provide the center module, thus odd leftover lengths may be combined without loss of any of the material to provide the center module.

The abbreviations for the dimensions discussed in the foregoing and as noted in the chart below are'shown in FIG. 5, wherein:

F is the overall width of the pulley; B is the belt width; A is the length of the flat surface of the lagging which comprises CS, length of center section, plus 2 X F E, the length of flat portions on end sections; L is the length of end sections; EC is the length of edge crown on end sections; C is the length of belt engaged on edge crown; and T is the constant thickness of flat portion of lagging. A third size of end member 12-13 will provide a proportionally larger range of pulley size within the specified belt-training-to-beltlife relationship.

DIMENSIONS IN INCHES EC FE L I claim:

1. In a traction-face structure for a smooth flat belt driving pulley face, said structure having a plurality of circumferentially spaced axially extending initially separate traction sections formed for side-by-side placement circumferentially of a pulley face, the improvement providing the conversion of any of a plurality of said pulley faces of different axially extending widths to an edge-crown shape and comprising:

each of said sections consisting of three end-to-end axially extending components comprising:

a center component formed to provide over its length a substantially constant belt gripping diameter and constructed for cutting into various lengths for different width pulleys; and a pair of opposite end components formed to provide a relatively reduced belt gripping diameter.

2. The improvement of claim 1, the thickness 6? said 2 "s'aneiaaaravanm of Brain" 2155i? "Cam anile having length such that the ratio of the length of said constant belt gripping diameter to the total belt gripping length both measured axially of said pulley face is in the range of about 0.5 to about 0.7.

4. The improvement of claim 3, said end components having length portions contiguous to said center component of a substantially constant thickness substantially the same as said center component whereby the length of said constant belt gripping diameter is extended onto said end components.

5. The improvement of clairn 3 said components each comprising a backing plate adapted for mounting on said pulley face and a section of belt traction material on said plate with said plates projecting from said sections at the circumferentially opposite sides thereof to provide side flanges; and

a plurality of elongated strips adapted for securing to said pulley face parallel to the pulley axis and having a plurality of longitudinally spaced first portions positioned in abutment with the edge face of one of said flanges, and a plurality of longitudinally spaced second portions intermediate said first portions and radially offset therefrom and positioned in overlying relation to said last named flange. 

1. In a traction-face structure for a smooth flat belt driving pulley face, said structure having a plurality of circumferentially spaced axially extending initially separate traction sections formed for side-by-side placement circumferentially of a pulley face, the improvement providing the conversion of any of a plurality of said pulley faces of different axially extending widths to an edge-crown shape and comprising: each of said sections consisting of three end-to-end axially extending components comprising: a center component formed to provide over its length a substantially constant belt gripping diameter and constructed for cutting into various lengths for different width pulleys; and a pair of opposite end components formed to provide a relatively reduced belt gripping diameter.
 2. The improvement of claim 1, the thickness of said center component being substantially constant over its length to provide said constant belt gripping diameter; and the thickness of said end components at their ends contiguous to said center component being substantially the same as said thickness of said center component and being tapered to reduced thickness at their opposite ends to provide said reduced belt gripping diameter.
 3. The improvement of claim 2, said components having length such that the ratio of the length of said constant belt gripping diameter to the total belt gripping length both measured axially of said pulley face is in the range of about 0.5 to about 0.7.
 4. The improvement of claim 3, said end components having length portions contiguous to said center component of a substantially constant thickness substantially the same as said center component whereby the length of said constant belt gripping diameter is extended onto said end components.
 5. The improvement of claim 3, said components each comprising a backing plate adapted for mounting on said pulley face and a section of belt traction material on said plate with said plates projecting from said sections at the circumferentially opposite sides thereof to provide side flanges; and a plurality of elongated strips adapted for securing to said pulley face parallel to the pulley axis and having a plurality of longitudinally spaced first portions positioned in abutment with the edge face of one of said flanges, and a plurality of longitudinally spaced second portions intermediate said first portions and radially offset therefrom and positioned in overlying relation to said last named flange. 